Unique opportunity to study 12yo boy with pseudohypoaldosteronism, to determine 1) his sodium and potassium replacement requirements, 2) the effect of variations in intake of these ions on muscle function and endurance, 3) the effect of an angiotensin converting enzyme inhibitor on electrolyte balance, and 4) the effect of oral K-exelate on the control of hyperkalemia. It is hoped this information will lead to improved care for this patient and better understanding of the treatment of this rare disorder.